Ulnar Claw - Ulnar Paradox

Ulnar Paradox

The ulnar nerve also innervates the ulnar (medial) half of the flexor digitorum profundus muscle (FDP). If the ulnar nerve lesion occurs more proximally (closer to the elbow), the flexor digitorum profundus muscle may also be denervated. As a result, flexion of the IP joints is weakened, which reduces the claw-like appearance of the hand. (Instead, the fourth and fifth fingers are simply paralyzed in their fully extended position.) This is called the "ulnar paradox" because one would normally expect a more proximal and thus debilitating injury to result in a more deformed appearance.

The other way to look at it: as reinnervation occurs along the ulnar nerve after a high lesion the deformity will get worse (FDP reinnervated) as the patient recovers - now that truly is a paradox! A simple way to remember this is: 'the closer the Paw, the worse the Claw'.